Duane A. Tolle

Microcosm/field comparison of trace element uptake in crops grown in fly ash-amended soil

Acidic (pH 4.98) precipitator fly ash was mixed with the topsoil of a nearly neutral Crosby silt-loam soil in both laboratory microcosms and field plots. The objective was to evaluate the accuracy and reliability of intact microcosms to predict trace element enrichment in field-grown crops due to fly ash amendment. Laboratory and field experimental units were amended with fly ash at 0, 100, 400, and 700 MT/ha, prior to planting a mixed crop of alfalfa, timothy, and oats. Microcosms accurately predicted the enrichment ratios (ERs) of 22 out of the 25 trace elements analyzed in field-grown alfalfa. Boron was the only element which accumulated in plant tissue at levels reported to be toxic to plants and may have caused the yield declines in all plants at high fly ash treatment levels. Plant uptake of Mo, Se, and As, particularly at the highest fly ash amendment levels, was sufficient to make the crops hazardous as a forage for cattle or sheep. Intact agricultural microcosms are recommended for prediction of potential trace element uptake in the field associated with untested combinations of soil type, fly ash, and plant species.

Effects of fly ash on microbial C02 evolution from an agricultural soil

Unweathered, acidic fly ash from a coal-fired power plant was applied to alfalfa meal-amended agricultural soil at levels equivalent to 0, 100, 400, and 700 tonne ha−1. Amended soils were placed in respirometer jars and monitored for C02-C evolution over a 37-day period. Fly ash applications of 400 and 700 tonne ha−1 reduced C02-C production significantly compared to 0 and 100 tonne ha−1 treatments. Carbon dioxide-carbon from all treatments was considerably greater than that from soil treated with 1000 ppm CdCl2. The results suggest that soil heterotrophic microbial activity may be impacted minimally by relatively low levels of fly ash application, but may be inhibited by higher levels of fly ash. Several metals were present at potentially toxic levels in the fly ash employed and may have accounted for the inhibition of CO2 C evolution. The availability of some of these metals was indicated in companion plant uptake experiments.

Regional scaling and normalization in LCIA

Methodologies for regional scaling and normalization steps in life-cycle impact assessment (LCIA) were developed and applied to two case studies in connection with the equivalency factor type of hazard characterization approach. Regional scaling factors are numerical scores used to indicate ranges of the degree of sensitivity that a particular region has for the selected impact category. These factors were developed to modify and improve the accuracy of partial equivalency factors for five impact categories. Normalization is the process of defining the relative contribution of the characterization scores by impact category to the total impact for the same category. Normalization factors were developed that represent the total, annual, geographically relevant, impact potential (hazard potential from emission loading or resource use) for a given impact category. Global or U.S. data were obtained to develop normalization factors representing 14 impact categories considered to be relevant to three spatial areas: global, state, and facility. The regional scaling and normalization methods improved the ability to evaluate two LCIA case studies in the U.S. and increased the accuracy of conclusions about which alternative processes or individual impact categories had the greatest potential hazard for environmental effects.

Fate of sludge-applied silicones in agricultural soil microcosms

Our previous publications showed that silicone (polydimethylsiloxane, or PDMS) polymers degrade to monomeric silanols and eventually to C02 in laboratory soil incubations. In this study, 200 cs14C-PDMS was added to soil microcosms (Tuscola sandy loam and Fargo silty clay) in anaerobically digested sludge. Soybeans followed by wheat were grown for 7 months during which microcosms were subjected to 3 leaching events. Recoveries of14C in the microcosms ranged from 47 to 90%. The recovered14C was almost completely in the soils, with trace amounts in leachate and ≤ 2% of the total in plant shoots. Extraction of soils coupled with HPLC-GPC showed that the majority of soill4C was still polymeric, but with lower molecular weight than the original PDMS. From 1 to 5% of the remaining14C was probably small silanols. Results thus confirm laboratory studies and show that PDMS degradation occurs under conditions similar to the field.

Ecological effects of PDMS-augmented sludge amended to agricultural microcosms

The potential ecological effects of polydimethylsiloxane (PDMS)-augmented sewage sludge resulting from use of the sludge as an agricultural amendment were evaluated in a preliminary pot test and a definitive test in intact, agricultural soil-core microcosms. Seed germination and early seedling survival were evaluated in the pot study. The parameters investigated in microcosms included soil microorganism populations, crop productivity, and nutrient loss in soil leachate. Intact, soil-core microcosms from two soil types (silty clay or sandy loam) were amended with PDMS-augmented sludge by single or multiple (4) applications. Micrososms were sequentially cropped with spring wheat (Triticum aestivum) followed by soybeans (Glycine max). Ecological effects comparisons were made between microcosms containing one of three PDMS treatment levels in the sludge ( ∼ 290, 1000, or 3500 p.p.m.) and control microcosms containing sludge without PDMS. The three treatments of PDMS in sludge tested had no effect on seed germination and seedling survival when incorporated into soil (< 13 p.p.m. PDMS) in pots. Furthermore, PDMS in sludge amended to microcosm topsoil (< 10 p.p.m. PDMS) appears to have no effect on: (1) cumulative loss of nitrate-nitrogen in leachate; (2) oven-dry biomass of spring wheat or soybeans; (3) Rhizobium bacteria, as indicated by the number of nodules on soybean roots in sandy loam soil; and (4) numbers of soil microorganisms, including bacteria, actinomycetes, and fungi. However, the quantity and timing of sludge amendment may affect (1) loss of nitrate-nitrogen in leachate and (2) soybean yields.

A unique laboratory method for evaluating agro-ecosystem effects of an industrial waste product

SummaryThis paper describes the design, extraction, and maintenance of intact soil-core microcosms which accurately predicted biomass reduction, nutrient loss and trace element enrichment in field-grown crops amended with acidic precipitator fly ash. These agricultural microcosms sustain ecosystem-level interactions while offering a cost-effective, manageable, experimental unit which can be subjected to laboratory controls.

Streamlined LCA of Soy-Based Ink Printing

This study provides a benchmark of the life cycle environmental impact characteristics associated with a typical soybased ink used for sheetfed lithographic printing. The scope ineluded a streamlined Life Cycle Inventory (LCI) and Impact Assessment (LCIA). Materials, processes, and life cycle stages that are the same between different printing inks, or were less than one percent by mass of the printing system input materials, were excluded. The LCIA included identification of specific processes in the life cycle of soy-based ink printing that make the greatest contribution to the overall environmental hazard potential in 13 impact categories for the baseline printing system selected. The LCIA approach included both regional scaling for areas that differ in sensitivity to certain impact indicators and normalization against a reference value. Reduction in the use of tall oil rosin and switching from conventional to low or no-till farming appear to be promising opportunities for reducing the environmental hazard potential.

Life cycle assessment of chemical agent resistant coatings

The Department of Defense (DoD) and the U.S. Environmental Protection Agency (EPA) have established a history of cooperation on a wide variety of pollution prevention research efforts, which apply the principles of Life-Cycle Engineering and Design (LCED) to DoD operations. DoD and EPA jointly sponsored this project, with funding from EPA and DoD’s Strategic Environmental Research and Development Program (SERDP), to focus on using Life Cycle Assessment (LCA) principles for optimizing the process of painting military vehicles with chemical agent resistant coatings (CARC). The objectives were to identify environmental and energy burdens of the CARC painting life cycle, and to identify and test potential improvements on a life cycle basis.This LCA of CARC includes difficulties and lessons learned while conducting all three LCA components. The streamlined life-cycle inventory (LCI) involved quantification of environmental and energy burdens associated with the CARC life cycle. Based on the results of the LCI, a preliminary scoping of potential impacts, and a knowledge of alternative CARC painting materials and equipment, five alternatives for the application of CARC were identified. The life-cycle impact assessment (LCIA) of these applications used the equivalency method for impact characterization. The life-cycle improvement assessment (LCImA) results suggested that one application, based on combining an alternative primer and the turbine high-velocity, low-pressure (HVLP) spray painting system, should be subjected to test and evaluation. The LCIA gave this alternative the lowest environmental impact potential scores for seven of nine impact categories compared to the five other alternative systems evaluated. The preferred alternative was technically evaluated in the laboratory against the baseline CARC system using test panels painted at two Army bases. Preliminary results indicate that the preferred alternative performs equal or better than the baseline system at lower cost and with reduced environmental impact potential.

Comparison of two equivalency factor approaches with simplified risk assessment for lcia of toxicity impact potential

Three approaches recommended for characterization of toxicity impact potential in a life cycle impact assessment (LCIA) are tested on a case study and compared. The two equivalency factor methods are the Persistence, Bioaccumulation, and Toxicity (PBT) method and the Multimedia Fate Modeling (MFM) method using a Mackay Level III model with state-specific environmental data. The simplified risk assessment (SRA) method involved dispersion modeling using site-specific environmental data. The life cycle inventory information evaluated by all three methods was limited to manufacturing of the RDX-based explosive in Kingsport, Tennessee. The effort to collect site-specific environmental data and conduct air dispersion modeling for the SRA method required about 24 times more effort than the PBT method and about 4 times more effort than the MFM method. Direct comparison of impact potential scores for the three approaches were limited to inhalation toxicity scores for nine air pollutants modeled by SRA. Correlations were made on the rank order of the impact potential scores for the nine air emissions evaluated for all three LCIA methods. Although the number of chemicals compared is very limited, the best correlation coefficient (0.96) was between the rank orders for the MFM and the SRA methods. The minimal effort and reduced accuracy of the PBT approach make it best suited for screening large numbers of chemicals for further evaluation of the highest ranked chemicals. The intermediate effort and reasonable accuracy (includes transfers to other media) of the MFM approach make it well suited for LCIAs involving comparative assertions or governmental policy decisions. The maximum effort and assumption of highest accuracy make the SRA approach suitable only after limiting the locations of interest to a few sites by screening with the other two approaches.